EO2401, a novel microbiome-derived therapeutic vaccine for patients with adrenocortical carcinoma (ACC): Preliminary results of the SPENCER study.
Authors: Eric Baudin, Camilo Jimenez, Martin Fassnacht, Salvatore Grisanti, Catharina Wilhelmina Menke, Harm Haak, Vivek Subbiah, Jaume Capdevila, Christelle De La Fouchardiere, Dan Granberg, Gedske Daugaard, Otilia Kimpel, Matthias Kroiss, Livia Lamartina, Laurent Chêne, Jean-Michel Paillarse, Alfredo Berruti
Journal: Journal of Clinical Oncology (2022)

4596 Background: In advanced ACC, no significant progress has been made since introduction of mitotane and cisplatin-based therapy. EO2401 (EO) was designed to activate existing commensal memory T cells cross-reacting with tumor associated antigens (TAAs). EO includes microbial-derived, synthetically produced peptides corresponding to HLA-A2 restricted epitopes with molecular mimicry to three TAAs upregulated in ACC, IL13Rα2, BIRC5 and FOXM1, with the CD4 helper peptide UCP2 and the adjuvant Montanide. Pre-clinically EO generates strong immune responses and cross-reactive CD8 cells recognizing the TAAs. Methods: This Phase 1/2 trial (NCT04187404) investigated EO + nivolumab (N) (EO + N = EN) in pts with ACC. Cohort 1 lead-in established safety of EN. Cohort 2 includes pts with metastatic ACC, with (C2a), or without (C2b) prior systemic therapy. EN was given 4 times q2 w, followed by boosters q4 w until PD (iRECIST). Results: 33 pts with ACC started study treatment: C2a 26 pts (58% 1; 42% 2 prior lines), C2b 7 pts. Median age 47; 24% men; ECOG 0/52%, 1/42%, 2/6%; 61% ≥2 organs involved by metastases (61% liver, 76% lung). EN was well tolerated. The combination safety profile was consistent with the profile of N monotherapy except for higher local administration site reactions (any erythema/pain/induration in 35% of pts). Overall (n = 33), best RECIST response was PR 12%, SD 24%, PD 45%, NE 18%; median PFS was 1.9 mo (range 0.4-7.6+); median survival not reached, and survival rate at 6-mo 63% (median FU 4.9 mo, range 0.9-12.0). Strong CD8 T cell ELISPOT responses against the vaccine peptides (9/9 pts) and cross-reactivity against targeted TAAs (8/8 evaluable pts) was observed. Tetramer staining of specific CD8 cells for all 3 peptides was detected in 7/8 tested. When investigated, positive staining against BIRC5 was detected as early as 4 w after the first vaccination. In C2a, a group of pts (n = 10) with SD at the first CT (incl. 4 pts with PR) seemed to fare well; all investigated tumor samples in this group showed a low level of TMB, low MSI, and low PDL1 expression. In contrast, 10 pts had PD &lt; 2mo and died &lt; 6mo. There was no correlation between clinical benefit and a large panel of cytokines/chemokines. However, post-hoc analysis identified several clinical factors (prior mitotane, ECOG ≤ 1, ACC 1st diagnosis &gt; 9 mo, max lesion ≤125 mm, ≤3 organs involved, lymphocytes ≤ grade 1) that excluded 90% of pts without benefit to EN. In the post-hoc selected group (n = 14) with median FU 6.9 mo (12 pts censored) the DCR was 64% (4 PR, 5 SD), 6-mo PFS was 42% and 6-mo survival rate 93%. Conclusions: EO2401 in combination with nivolumab was well tolerated and induced a specific immune response in all tested pts. In addition, efficacy was seen in a subpopulation of pts with ACC defined by clinical parameters in a post-hoc analysis. A randomized phase 2 study based on the findings of Cohort 2a is being planned. Clinical trial information: NCT04187404.